Hans Eysenck - Psychology of Personality - The Canon

Psychology: Essential Thinkers, Classic Theories, and How They Inform Your World - Andrea Bonior 2016

Hans Eysenck
Psychology of Personality
The Canon


BORN 1916, Berlin, German Empire


DIED 1997, London, England


Educated at University College, London



Hans Eysenck had myriad interests within psychology, and his prolific writings include treatises on intelligence testing, behavior therapy, physiology, and genetics. But his biggest legacy remains in the field of personality psychology, where he used empirical and statistical techniques like factor analysis to identify certain personality dimensions that help describe how we differ from each other.

Factor analysis involves taking large amounts of data and looking for cohesive categories—factors—that are found to be statistically salient. One does this by examining the correlation between every single pair of data points and seeing which ones tend to go together. Factor analysis became a popular source of study for personality psychologists and often started with the language that has been developed to refer to personality traits. You could take lists and lists of words that we use and start to assess which ones tend to overlap in terms of how they describe someone. Well-mannered and polite might correlate with each other rather closely, for example, whereas affectionate might overlap some but also speak to a different quality altogether, and kind might be in the middle of all of them.

Eysenck dared to narrow personality traits down to only two main factors, which he believed to encompass who we are: introversion/extraversion and neuroticism. The former involves characteristics that he expanded upon after the work of Carl Jung, even though Eysenck was a very forceful opponent of psychoanalysis. The latter factor, neuroticism, involves one’s level of emotional stability (or emotional instability). Eysenck saw these two dimensions as independent of each other, and they could be viewed as intersecting axes, offering the ability to plot personality into different quadrants. And he gave each of those quadrants a name corresponding to the temperaments that had been identified by Hippocrates more than 2,000 years before: melancholic (prone to the blues), choleric (hotheaded), phlegmatic (calm and reserved), and sanguine (cheerful). Of course, in Hippocrates’s definition, these personality types were directly attributable to the individualized levels of bodily fluids that people supposedly carry around: black bile, yellow bile, phlegm, and blood, respectively. Eysenck did not subscribe to that particular theory, but he recognized that physiology plays a role in personality, and he believed that such personality types tend to be genetically ingrained.

Eysenck looked toward biology to explore this concept further and to help explain how what was happening in our particular bodies can turn us into the types of people we are. For example, he hypothesized that neuroticism has to do with how sensitive the sympathetic nervous system is: Highly neurotic (or anxious) people, he said, have an overactive sympathetic nervous system that goes into fight-or-flight mode at the slightest provocation. We’ve all felt the body preparing for action (or freezing in terror) in moments of fear—the heart rate increases, breathing gets faster, and the hair on the arms may stand on end.

Eysenck’s theories of introversion and extraversion went beyond Jung’s and into biology as well. According to Eysenck, this dimension involves excitation and inhibition and what we do to negotiate the balance between these two ends of the spectrum. To Eysenck, excitation meant increased alertness, with the brain at full attention. Inhibition was the opposite, with the brain trying to calm itself down by blocking out stimuli or even going to sleep. Eysenck said that the more extraverted someone is, the stronger his or her inhibition processes. That sounds counterintuitive, as we tend to think of inhibition in terms of being behaviorally inhibited—being too shy to talk to someone, or being too anxious to express our true selves. But remember that Eysenck was talking about physiological inhibition, not behavioral inhibition—he was referring to how our bodies inhibit arousal—and so the higher the inhibition, the greater the ability to keep from becoming overly anxious, and thus the greater the ability to attune to the outer world (like an extravert) without withdrawing into the self (like an introvert).

Eysenck’s theory said that this is why the differences between extraverts and introverts are seen not just in how people react to other individuals but also in how they respond to their environment. Extraverts can often study in the presence of background noise without becoming overstimulated, perhaps even preferring some white noise. Extraverts, it has been suggested, also perform better with caffeine than introverts do and are happy to have a lot of information thrown at them when they’re making decisions. This is all because it is harder to overtax their nervous systems, and they have a higher threshold to reach before feeling overexcited.


Trait theories of personality are not without their detractors, and the question of how much personality trumps situational context is one that persists to this day (and underlies the differences between the psychology of personality and social psychology). Furthermore, the notion that genetic factors overwhelmingly cause these differences is no longer as certain today. Eysencks’s focus on genetics also led him down the controversial and disputed path of suggesting that racial differences in intelligence may be widespread and inherited. Nonetheless, Eysenck’s use of statistical techniques and physiological findings to validate personality distinctions was a big step forward for the field.

After a period of focusing only on his main two personality factors, Eysenck realized that there might be samples of populations that he was not dipping into. So he collected data among those who were hospitalized in psychiatric institutions. Eventually this led to his adding the dimension of psychoticism, which to him meant aggressive, impulsive, and antisocial attributes. (This is not to be confused with the purer modern definition of psychosis, which refers more specifically to the experience of hallucination and delusions.)


Eysenck’s personality research paved the way for further exploration of physiology and behavior, and for further trait theories of personality. He was instrumental in arguing for the importance of genetic influences on personality and for the importance of measurement in psychological research. He also espoused some offensive and controversial views, such as the idea that the alignment of the planets at one’s birth affects personality, and the notion that the development of cancer among smokers is less linked to cigarettes than to the interaction of smoking with personality and constitutional factors.


When you think of your friends and loved ones, you may have a very good idea of how you would rate them in terms of introversion and extraversion, and emotional stability versus instability. As brief and simple as these two categories may seem, though, if you combined them to create the quadrants that Eysenck defined, you might be surprised by just how many characteristics they encompass.

The melancholic personality—high in instability and introversion—could be seen as quiet, pessimistic, rigid, and moody. Surely we know people like this. Some of them, though troubled, even seem to be particularly talented: brooding artists, tortured writers, singers who have been in a permanent dark phase. They are tuned in to their own thoughts, but living among those thoughts is not a particularly calm experience. Things are stormy. And yet they may retreat from the world, further into their own feelings, which might distress them enough to retreat even further and then, perhaps, find ways of expressing themselves to help with some of the distress.

Now let’s visualize the choleric personality: high in both extraversion and instability. Here, the distress seen in the melancholic personality is turned outward. Maybe you know someone, a fully grown adult, who is prone to tantrums, quick to anger, and chronically tense: one little slip-up from someone else, and such people blow their stacks. Perhaps they have chronic road rage or are prone to getting into online fights with people who disagree with them politically. Like melancholic personalities, such people are unstable—the storm inside them is brewing—but they are more externally oriented. They are extraverts, not in the sense of being charming and popular, but in the sense of always being focused outside themselves.

The phlegmatic personalities—high in introversion and low in instability— are not often raising people’s hackles as the choleric type does, but they’re also probably not often on people’s radar. Attuned inward, and not particularly driven by bouts of emotion, they are likely rather quiet and unassuming. Eysenck was not particularly complimentary of this type (the sanguine type alone got a thumbs-up from him) in that he described phlegmatic personalities as also tending toward laziness and passivity. We all may know plenty of perfectly pleasant people in this category, but they tend not to be particularly noticeable. They might move slowly through life because they lack the jolt of varying emotions.

Finally, the sanguine personalities—high in extraversion and low in instability—are comfortable with themselves and not prone to outbursts. They are often optimistic and even bubbly, maintaining an even keel but being interested in the world around them. If you know any people like this, you’ve probably noticed that their social calendars are fairly full, in part because other people want to be around them.

Although we all know people who fit these types, it’s important to remember that Eysenck recognized the dimensional nature of the traits represented by his quadrants; he delineated these four personality types along an x-y axis, so they touch each other, and it’s possible for someone to be anywhere within a particular quadrant. In recent years, we have seen more of a focus on the undeserved bad rap that introverts get. It is true that in these groupings, Eysenck seems to have associated introversion a bit more with unhealthy qualities, perhaps because of its association with the physiological aspects of needing to tune out the world. Though we might tend to think of introversion more favorably today, Eysenck’s types and their physiological underpinnings are a great starting point for thinking about what makes us tick.